ProXs drive the formation of membraneless organelles in plants

Membraneless organelles (MLOs) are non-membranous structures inside cells that organize cellular space and processes. The recent discovery that MLOs can be assembled via liquid-liquid phase separation (LLPS) advanced our understanding of these structures. However, the proteins that are capable of forming MLOs are largely unknown, especially in plants. In this study, we developed a method to identify proteins that we referred as ProXs (Proteins enriched by b-isoX) in Arabidopsis. Heterologous expression in yeast cells showed that most ProXs were capable of forming MLOs autonomously. We applied this method to several model and crop species including early and higher plants. This allowed us to generate an atlas of ProXs for studying plant MLOs. Analysis of ProXs from different species revealed high degree of conservation, supporting that they play important roles in cellular functions and are positively selected during evolution. Our method will be a valuable tool to characterize novel MLOs from desired cells and the data generated in present study will be instrumental for the plant research community to investigate MLO biology.